One student group varied the pH of the yeast mixture. Their results can be seen here. Based on their data, the most desirable pH for fermentation is

The optimum pH for fermentation is between 5.5 and 6.0.

Explanation:

Fermentation can be described as a metabolic process in which the breakdown of organic matter occurs in microorganisms such as bacteria or yeast.

Yeast fermentation produces carbon dioxide and ethanol.

The fermentation process depends on certain factors such as the:

a) temperature

b) pH

c) amount of yeast

In the data collection shown in the question, we can see that when the temperature is kept at a constant i. e 25 degrees Celsius, the fermentation rate was the fastest when the pH of the experiment was 5.5 and 6.0. This means that the optimum pH for this fermentation process is between 5.5 to 6.0.